(1) Field of the Invention
The instant invention is directed to the field of direction finders, and more particularly, to such direction finders that provide improved bearing measurements when subjected to pivoting/tilting motion as from the effects of the sea surface typically encountered on ship, submarine mast, and expendable and towed buoy deployments.
(2) Description of the Prior Art
Existing submarine direction finders are mounted on masts which are raised from the sail when the submarine is either at periscope depth or on the surface. These devices are operative to determine the direction of arrival of incident electromagnetic radiation based on antenna amplitude and phase relationships as a function of azimuth. They assume that the mast is always vertical, but ignore any errors that would be introduced by tilting/pivoting motion of the mast. Unless the sea state is high, these errors are typically small for such mast mounted direction finders. But for direction finders mounted on expendable and towed buoys and other platforms that experience tilting/pivoting motion about all three Cartesian axes, the heretofore known direction finders are subject to errors and compromised direction of arrival determinations to a degree that depends on the magnitude of the sea state and on the stability of the particular platform.